What you describe is not strange at all. In fact, it's common practice to wire the neutral and ground wires to the same bar. Take a look at panels with romex wiring - the greens and whites terminate on the same bar in most cases. The reason is that the ground and neutral serve the same function - to complete the circuit to ground. With the neutral, the circuit is completed when you flip the switch. With the ground, the circuit is completed when there's a fault (the hot wire breaks and touches the chassis, e.g.). So both N/G terminate, ultimately, in the same place.
On previous posts, I suggested wiring N/G on seperate bus bars in the panel. Two reasons: one is that today's electronics generate harmonics (additional current) and feed the neutral. Second is that induced current from EM/RFI can be picked up by ground wire planes. By separating the two, their respective currents will (hopefully) be drained to ground, reducing the probability of common-mode noise.
But if all you want to do is run power to the garage, then simply install a new breaker, run the black, white and green (if required) wires underground to the garage and connect the outlet. Connect the ground wire and the neutral to the N/G combo-bus in the panel. It will work fine. Just check with local codes for the proper raceways they allow for outside power feeds. If metallic raceways are permitted, then the raceway itself is the ground - just bond it to the panel with the appropriate hardware (locking collar, bonding screw, etc.). If PVC or plastic is required, then you'll need the green ground wire.
One other thing: distance is a factor with respect to voltage drop. Freezer motors don't like low voltages (tough on start-up) so if you're going more than 50 feet, use #10 wire instead of standard #12 or #14. And install GFCI outlets in the garage whether the code requires them or not.
On previous posts, I suggested wiring N/G on seperate bus bars in the panel. Two reasons: one is that today's electronics generate harmonics (additional current) and feed the neutral. Second is that induced current from EM/RFI can be picked up by ground wire planes. By separating the two, their respective currents will (hopefully) be drained to ground, reducing the probability of common-mode noise.
But if all you want to do is run power to the garage, then simply install a new breaker, run the black, white and green (if required) wires underground to the garage and connect the outlet. Connect the ground wire and the neutral to the N/G combo-bus in the panel. It will work fine. Just check with local codes for the proper raceways they allow for outside power feeds. If metallic raceways are permitted, then the raceway itself is the ground - just bond it to the panel with the appropriate hardware (locking collar, bonding screw, etc.). If PVC or plastic is required, then you'll need the green ground wire.
One other thing: distance is a factor with respect to voltage drop. Freezer motors don't like low voltages (tough on start-up) so if you're going more than 50 feet, use #10 wire instead of standard #12 or #14. And install GFCI outlets in the garage whether the code requires them or not.