Yes, It's possible to gain 10lb LBM and more without steroids.
With a diet of Low GI carbs, good fat and lots of protein will make you add 10lb, while holding fat away. One thing though, It will take some time...Do your morningcardio and wait 1 hour postworkout before you eat anything and you will be able to gain the mass. I'm an Easygainer my self(don't know if you are..) so for me a low GI diet, lots of protein(2g per LB) and healty fat helps me adding mass and to keep fat away. I do my morning cardio 4 times per week and workout 4 times per week in the gym. If I eat to much of the high GI carbs I will start adding fat like crazy. There are as I wrote a few TIPS and TRIX you can use while bulking to keep the fat away. Low GI carbs, Flax Seed oil, High protein(casein before bedtime, whey one hour post workout), morning cardio and also to wait one hour post workout before you eat. This will help you burn fat away. For me this really helps, and maybe also for you. Do not overtrain, when you feel burned out, tired and lack of energi, then take a break. If you notice that you are gaining more and more fat, then take a week off from the bulking and start cutting(just lower calorie intake) and in the end of the cuttingweek, you will have lost the fat you gained(you wont loose any muscles in a week if you are eating like you should and not overdoing cardio).
Hope this helps..(sorry for the spelling)