The game allows the player to control one of 12 teams in either a single game or a full season. For single games, there is also a two-player option.
Bases Loaded featured a television-style depiction of the pitcher-batter matchup (previously seen in Intellivision World Series Baseball and Accolade's HardBall!), as well as strong play control and a relatively high degree of realism, which made it one of the most popular baseball games of the early NES.
One unique feature of the game is that the pitcher can provoke a batter to charge the mound. Each team has only one batter (usually the team's best hitter) who can be provoked in this manner, however; it is up to the player to discover who it is.
At the time Bases Loaded was released, few video games were licensed by North American major league sports. Therefore, the league depicted in Bases Loaded is a fictitious league of twelve teams. They are:
Boston - has above-average starting pitching with Bopper, Fine, and Page; a strong bullpen; and a powerful lineup powered by Freida, Norkus, and Angel
D.C. - carries a great offense led by Doreo, Fendy, and Boro but has below-average starting pitching and an average bullpen with the exception of the practically unhittable Hall. If the controller is used properly, Hall will strike out just about everyone until the 5th or 6th inning.
Hawaii- has a strong hitting lineup led by Brutus, Debro, and Moon; reasonable starting pitching; and an average bullpen
Jersey - boasts the most explosive offense in the game anchored by Paste (best hitter in the game with a .467 average and 60 home runs), Bay, and Ford but has starting and relief pitching that is average at best, unreliable at worst.
Kansas - features a starting rotation led by Patson, who has the fastest fastball in the game (102 mph) and good relief pitching, but an average offense, led by Patty and Baker, that has decent power but low hitting averages
L.A. - features a lineup with decent hitting averages but little power led by Wales and Bacon but has an average starting rotation led by Tucker and mediocre bullpen
Miami- holds the best starting pitching rotation with Henter (best pitcher in the game with a 1.85 earned run average), West, and Jarvis; average bullpen led by closer Irving; and weak offense led by Warner
N.Y. - has a great starting rotation of Carter, Howe, and Cora; an excellent bullpen led by Errico and Fiore; and a starting lineup led by Star that lacks some home run power but hits solidly throughout
Omaha- has average starting pitching led by Rennor, fair bullpen, and below-average lineup led by Lyonse and Carus
Philly - boasts the best overall pitching staff with the second best starting rotation with Gantos, Car, and Rush; the best bullpen led by Ellis; and a lineup with a solid middle of the order of Evans, Oko, and Rubin but otherwise average offense
Texas - has a high hitting offense anchored by Marcus but a very porous pitching staff
Utah- has one of the best offenses in the game led by Agua and Harlan, featuring a Jekyll and Hyde pitching staff with a strong starting pitching rotation led by Quinta, Lep, and Stava and an inconsistent bullpen led by Bella, one of the best closers in the game, but also features three of the five worst earned run averages.