He went 37-30 with a 3.07 earned run average and 519 strikeouts over five seasons in the Reds' farm system to earn a mid season call up to the majors in. He was completely dismantled by the Houston Astros in his major league debut. Making the start, he faced seven batters, retiring just one. He was pulled with four runs already across the plate, and runners on first and second. RelieverMario Soto allowed both inherited runners to score before retiring the new two, giving Berenyi six earned runs in just a third of an inning. He earned his first career win against the New York Mets on July 18. He held the Mets scoreless with seven strikeouts through seven before allowing the first three batters he faced in the eighth to reach. The Mets had pushed a run across, and had runners on first and third when Berenyi exited the game in favor of Tom Hume. Hume allowed both inherited runners to score, giving Berenyi three earned runs in seven innings on the day. Young starters Berenyi, Soto, Frank Pastore and Mike LaCoss behind veteran future Hall of FamerTom Seaver pitched the 1981 Reds to a Major League Baseball best 66-41 record. Berenyi was 4-2 with a 5.01 ERA when he pitched a one hitshutout against the Montreal Expos to lower his ERA to 4.31 as the players headed into the strike. Berenyi ran into some hard luck in the second half of the season. He was just 4-4 despite dropping his ERA to 2.64. Overall, he was 9-6 with a 3.50 ERA and 106 strikeouts in twenty starts. His 77 walks led the National League. Berenyi got off to a 4-1 start in April before hard luck began to haunt him once again. He went 1-8 over his next thirteen games despite an ERA that was only slightly above 4.00. After a decent stretch after the All-Star break, Berenyi lost his next eight decisions in a row with a 3.84 ERA. He was the losing pitcher on August 14 against the Astros despite not allowing an earned run. He also did not allow an earned run in his next start, and got a no decision. He shutout the Astros for his ninth and final win of the season on September 24. He had a league worst eighteen losses for a Reds team that was last in the major leagues in scoring and slugging, and lost 101 games. After a season that saw Berenyi go 9-14 with a 3.86 ERA, he began requesting a trade. Off season rumors of deals to the Tigers and New York Yankees never materialized, and he went into the season still with the Reds. In the second game of the season, he pitched six strong innings, allowing two runs, but the Reds team that scored eight runs for Mario Soto in the season opener was shutout with Berenyi on the mound. On May 5, Berenyi faced five batters, and failed to record an out in a start against the Philadelphia Phillies. On May 19, he faced five St. Louis Cardinals batters, and failed to record an out. He wast 3-7 with an even 6.00 ERA on June 15 when the Reds traded him to the Mets for minor leaguers Jay Tibbs, Eddie Williams and Matt Bullinger.
Thanks to its core of young prospects, the perennial cellar dwelling Mets were a surprising 33-25 when Berenyi joined them. The Mets released veteran Mike Torrez in order to make room for Berenyi in their starting rotation, making Berenyi the Mets' oldest starter at 29 years old. He lost his first Mets start, but rebounded in his second, pitching seven shutout innings against the Expos before handing the ball to Doug Sisk. As a Met, he went 9-6 with a 3.76 ERA. Despite his only being with the Mets for half a season, 1984 turned out to be the year he made the most appearances with his new club. In his first start of against Mario Soto and the Reds, he pitched seven innings of one hit, one walk ball. He pitched two innings into his third start of the season before being lifted with shoulder pain. He would undergo arthroscopic shoulder surgery that would sideline him for the remainder of the season. The Mets used a slow approach with Berenyi in. He made four appearances out of the bullpen, pitching 5.1 innings, before making his first start. He would make seven starts, never pitching more than six innings before being reassigned to the triple ATidewater Tides. He went 2-6 with a 6.61 ERA at Tidewater. The Mets released Berenyi following the 1986 World Series. He signed as a Free agent with the Expos prior to Spring training, but failed to make the club.
