Houston quarterback Jim Kelly completed 29 of 40 passes for 404 yards and four touchdowns to lead the Gamblers to a 42-7 victory yesterday over the Oakland Invaders in a U.S. Football League Western Conference game in Oakland.

The victory improved Houston's record to 3-0. Oakland fell to 1-1-1.

Kelly, who had totaled 835 yards and nine touchdowns in two games, battered the Invaders' defense for much of yesterday's game.

After leading the Gamblers to a 21-7 halftime margin, Kelly made Oakland pay for two mistakes in the second half.

On the opening possession of the half, the Invaders -- behind reserve quarterback Fred Besana -- drove from their 35-yard line to the Houston 33. However, on fourth-and-two, fullback Tom Newton was held for no gain.

Kelly then completed a five-yard pass to Richard Johnson and a 46-yard pass to Scott McGhee. Two plays later, Kelly hit McGhee for an eight-yard touchdown.

In the fourth quarter, Besana threw into double coverage and was intercepted by defensive back Luther Bradley. Three completions later, Kelly threw a 23-yard scoring pass to Clarence Verdin.

Kelly had touchdown passes of 34 yards to Johnson and 74 yards to Verdin in the first half.

Oakland's Albert Bentley scored on a six-yard run for his team's only score.